Method to promote growth of a plant

ABSTRACT

A concise method to promote growth of a plant useful for increase of food production. This invention provides a method to promote growth of a plant by administration of formic acid, an organic acid with a low molecular weight through avoidance of photo-oxidation damage. This invention also provides amino acid sequence of formate dehydrogenase and base sequence encoding the enzyme. The expression of the enzyme is induced by administration of formic acid and the enzyme is involved in metabolism, of formic acid and its salts. Furthermore, this invention provides a method to promote growth of a plant by administration of methanol through avoidance of photo-oxidation damage.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to a method to promote growth of a plant by administration of an organic acid with a low molecular weight to avoid photo-oxidation damage of the plant. This invention also relates to a method to promote growth of a plant by administration of an alcohol to avoid photo-oxidation damage of the plant.

[0003] 2. Description of Related Art

[0004] Nowadays, shortage of food production have became a serious problem because of population explosion throughout the world. Growth and metabolism of a plant are affected by various conditions of surroundings. Photo-oxidation damage is caused by alteration of surrounding conditions and triggered by decrease of carbon dioxide uptake, through closure of stoma under condition of strong light-intensity and droughtiness. Because of shortage of carbon dioxide under such condition, excess amount of energy is acquired by photosynthesis system. As the result, excess amount of active oxygen beyond defense ability of the plant is generated, which results in occurrence of the photo-oxidation damage. As such photo-oxidation damage inhibits plant growth, a method to prevent this phenomenon is desired. Heretofore, a transgenic plant having ability to delete active oxygen have been used for such purpose.

SUMMARY OF THE INVENTION

[0005] Despite of it, production of a transgenic plant with such characteristic takes much time and the range of plants suitable for producing such transgenic plant is limited. Therefore, the development of a method to prevent photo-oxidation damage with simplicity and wide-utility have been desired to promote growth of a plant.

[0006] It is known that, a plant metabolizes methanol and converts it to carbon dioxide, through formaldehyde and formic acid as the intermediate. Then the inventors administrated formic acid, an organic acid with a low molecular weight, to rice, tabacco and kidney bean and found avoidance of photo-oxidation damage. Moreover, the inventors have investigated effect of formic acid on growth of rice plant bodies and found its effectiveness on growth promotion. Moreover, the induction of formate dehydrogenase (FDH) activity, which metabolizes formic acid to produce carbon dioxide, was observed by administration of formic acid. Furthermore, the amino acid sequence of formate dehydrogenase (FDH) and the base sequence encoding the enzyme were determined. The photo-oxidation damage might be prevented by incorporation of FDH gene.

[0007] The inventors have also administrated methanol, an alcohol with a low molecular weight, to avoid photo-oxidation damage of rice, tabacco and kidney bean. Therefore, methanol might be effective for promotion of plant growth.

[0008] These and other features and advantages of this invention will become apparent upon a reading of the detailed description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009]FIG. 1 is a graph showing effects of various formate salts on photo-oxidation damage of rice.

[0010]FIG. 2 is a graph showing time course of photo-oxidation damage of rice and inhibition of photo-oxidation damage by potassium formate.

[0011]FIG. 3 is a graph showing effect of formic acid on photo-synthetic ability of rice under various intensities of illumination after photo-oxidation damage.

[0012]FIG. 4 is a graph showing dose-dependency of potassium formate concentration on inhibition of photo-oxidation damage of rice.

[0013]FIG. 5 is a graph showing inhibition of photo-oxidation damage of kidney bean by formate salts.

[0014]FIG. 6 is a graph showing inhibition of photo-oxidation damage of tabacco by formate salts.

[0015]FIG. 7 is a graph showing result of fluorescence analysis of rice after photo-oxidation damage.

[0016]FIG. 8 is a graph showing dose dependency of sodium formate concentration on wet weight of rice plant bodies.

[0017]FIG. 9 is a graph showing dose dependency of sodium formate concentration on height of aerial part of rice plant bodies.

[0018]FIG. 10 is a graph showing time course of formic acid uptake measured on rice.

[0019]FIG. 11 is a graph showing time course of carbon dioxide formation originated from formic acid measured on rice.

[0020]FIG. 12 is a graph showing activity of formate dehydrogenase measured on aerial part and ground part of rice plant bodies.

[0021]FIG. 13 is a graph showing amino acid sequence of rice formate dehydrogenase, compared with that of potato formate dehydrogenase and barley formate dehydrogenase.

[0022]FIG. 14 is a photograph of northern blotting, indicating alteration of FDH gene expression by administration of formic acid.

[0023]FIG. 15 is a graph showing effect of methanol and potassium formate on photo-oxidation damage of rice.

[0024]FIG. 16 is a graph showing effect of methanol on photosynthetic ability of rice under various intensities of light illumination.

[0025]FIG. 17 is a graph showing dose-dependency of methanol on inhibition of photo-oxidation damage of rice measured by fluorescence analysis.

[0026]FIG. 18 is a graph showing effect of methanol and formic acid on tabacco, measured by fluorescence analysis.

[0027]FIG. 19 is a graph showing effect of methanol and formic acid on kidney bean, measured by fluorescence analysis.

DETAILED DESCRIPTION OF EMBODIMENTS

[0028] (The Plant Bodies Utilized for the Experiments)

[0029] (1) Rice

[0030] The seeds of rice (Oryza sativa L.: Hinihikari) were used for the experiments. The plants were seeded under a vermiculight. They were grown under a light intensity of 150 μmol quanta/m².s for 16 hours in the light and 8 hours in the dark. Normal leaves derived from the plant bodies of 2 to 4 weeks old were used for the following experiments.

[0031] (2) Tabacco

[0032] The seeds of tabacco (Nicotina tabacum L.: SRI) were used for the experiment. The plants were seeded under a vermiculight. They were grown under the light intensity of 150 μmol quanta/m²·s. Normal leaves derived from the plant bodies of 4 to 6 weeks old were used for the experiments.

[0033] (3) Kidney Bean

[0034] The seeds of kidney bean (Phaseolus vulgaris L.: tsurunashiinngenn) were used for the experiments. The plants were seeded under a vermiculight. They were grown under the light intensity of 150 μmol quanta/m²·s. Normal leaves derived from the plant bodies of 2 to 4 weeks old were used for the experiments.

[0035] (Method for Administration of Sample Compounds)

[0036] In the case of rice plant, a portion containing petiole was excised from the plant bodies and it was immersed into 10 ml of sample compound in a tube. It was incubated for 30 min at 25° C. under 150 μmol quanta/m²·s of illumination. After administration of sample compounds, the leaves of rice were sliced and put in a chamber with diameter of 35 mm and the rate of oxygen generation (μmol O₂/m²·s) was estimated. In the case of other plants, a leaf disk with diameter of 35 mm was prepared prior to the experiment. It was immersed into 10 ml of sample solution in a dish and the sample solution was administrated under the same condition as rice plant. After the administration, water in the leaf disk was excluded, the leaf was set in the chamber and the ability of photosynthesis was measured on the leaf. Then, the sample solution was prepared by dissolving arbitrary amount of sample compounds into 10 mM potassium phosphate buffer (pH7) and sample solution thus prepared was used for the experiments. Potassium formate, sodium formate and ammonium formate were used for the sample compounds.

[0037] (Estimation of Photosynthetic Ability in Terms of Oxygen Generation Rate)

[0038] Generation of oxygen was measured by clark type oxygen electrode. The cuvette (LD2/2 type), the oxygen electrode controller (CB1-D3 type) and the light source (LS-2, Hansatec corp.) were adopted as components of the measuring device. The chamber of cuvette contained in this device is composed of combination of a chamber, capable of hermetically sealing with diameter of 35 mm and volume of 5 ml, and an oxygen electrode. As upper side of the chamber is transparent, arbitrary intensity of light can be illuminated. The plant body described above, after administration of formic acid, was enclosed in the chamber and sealed hermetically. It was illuminated using a halogen lamp as the light source, and the rate of oxygen generation was measured under the air containing 5% of carbon dioxide. Unless specified otherwise, the measurement was performed under the light adjusted to a intensity of 253 μmol quanta/m²·s using a red filter or an attenuation filter. The oxygen generation was calculated by dividing the obtained value with the surface area of the leaf.

[0039] (The Condition of Photo-oxidation Damage)

[0040] After measurement of rate of photosynthesis as described above, the air without carbon dioxide was introduced into the chamber and the light was illuminated at the intensity of 1600 μmol quanta/m²·s for a certain period. The photo-oxidation damage, caused by lack of carbon dioxide, was induced under the condition described above. The rate of oxygen generation was measured after this treatment and inhibition of photosynthetic ability caused by photo-oxidation damage was thus evaluated.

[0041] (The Effect of Formate Salts on Photo-oxidation Damage)

[0042] The effect of various formate salts on the photo-oxidation damage of rice was investigated. The rate of oxygen generation was reduced to about 30% by 8 min of strong light illumination in the absence of carbon dioxide as shown in FIG. 1. On the other hand, plant bodies retained 90% of oxygen generation activity by addition of 2 mM of potassium formate. Such protection effect was the most prominent on potassium formate. Two mM of formate salts exhibited potency on protection of oxygen generation ability in the turn of potassium formate, sodium formate and ammonium formate. Moreover, time course of protection of photo-oxidation damage by formate salts was investigated. Prolonged treatment (2 min, 4 min) of photo-oxidation damage caused damage on photosynthetic ability in a time dependent manner as shown in FIG. 2. Despite of it, the damage on photosynthetic ability was inhibited in the presence of 2 mM potassium formate.

[0043] Furthermore, the effect of light intensity on photosynthetic ability of rice sample was investigated after photo-oxidation damage treatment. As shown in FIG. 3, the inclination was not altered under weak light illumination, whereas the addition of formate salt inhibited damage on photosynthetic ability under strong light illumination. From this result, enzyme system concerning calvin cycle might be protected in the presence of formate salts. Moreover, the dose-dependency of potassium formate concentration on protection of photo-oxidation damage, caused by potassium formate, was investigated on rice. As the result, 2 mM or 4 mM of potassium formate exhibited optimum protection on photo-oxidation damage as shown in FIG. 4.

[0044] The effect of formate salts on photo-oxidation damage was also observed on kidney bean and tabacco. Administration of 2 mM of potassium formate exhibited inhibition on oxygen generation rate caused by photo-oxidation damage. FIG. 5 shows the result on kidney bean and FIG. 6 shows the result on tabacco plant.

[0045] (Fluorescence Measurement of Chlorophyl)

[0046] To estimate sanity of photo-system, the fluorescence originated from chlorophyl, the center of photo-system, was measured on rice under the same condition described above after photo-oxidation damage. The measurement was performed by chlorophyl fluorometer (PAM101: emitter and detector, PAM103: light pulse generator, WALTZ). The condition of measurement was as follows. Excitation: 100 KHz, intensity: 5, saturated light: 900 ms. The fluorescence was measured before and after photo-oxidation damage to estimate Fv/Fm value. The condition of plant growth, the method to administrate formic acid and the preparation of samples adopted in this experiment were the same as the experiments on oxygen generation. The result of fluorescence measurement revealed that damage on photo-system, caused by photo-oxidation damage, was avoided by addition of 2 mM formate (FIG. 7).

[0047] (Plant Growth Test)

[0048] The effect of formate salts addition observed on plant growth was investigated. The seeds of rice were sterilized and seeded into a glass tube (130 mm×40 mm I.D) containing medium described below. The contents of the medium are ½ MS salt, 0.1% gellan gum and various concentrations of sodium formate. The pH was adjusted to 6.0 by addition of 1N sodium hydroxide and the medium was sterilized by autoclave treatment. The rice seeds were grown under 25° C. for 16 hours in the light and 8 hours in the dark, under 40 μmol quanta/m²·s of illumination. After cultivation for 2 weeks under this condition, the extent of growth was estimated by measurement of length of the aerial part and wet weight of plant bodies.

[0049] The effect of formate salts on growth of rice plant bodies, measured as described above, was investigated. The effect of sodium formate was investigated under various concentrations to reveal that, addition of 125 ppm of sodium formate resulted in 25% of growth promotion, both on wet weight of plant bodies (FIG. 8) and length of aerial part (FIG. 9). The growth promotion effect disappeared at the presence of 1000 ppm of sodium formate. The student t-test was performed on difference of average value calculated on 30 samples. The result showed significant difference at a significantly low level of less than 1%. Therefore, the formulation containing 125 ppm of sodium formate with pH adjusted to pH7 is effective for promotion of plant growth. Formic acid, the effective ingredient of this formulation, can be added to ordinal phosphate fertilizer or nitrogen fertilizer. As an example of such fertilizer, a commercial fertilizer “hyponex” is preferred.

[0050] (Uptake of Formic Acid into Plant Bodies)

[0051] To confirm metabolism of formic acid, uptake of formic acid into plant body was investigated under the condition described at “plant growth test”, using rice cultivated for 2 weeks at 25° C. Five plant bodies were harvested and washed by water, then 2.5 ml of 1.4 mM sodium formate was added and incubated under illuminated condition (40 μmol quanta/m²·s) at 25° C. Twenty-five μl of the solution was sampled at each period and formic acid concentration in the solution was determined by absorbance. The result exhibited rapid uptake of formic acid and formic acid was not detected in the solution after 48 hours. FIG. 10 shows the result as the average value of three independent experiments. Formic acid is assumed to be absorbed in the plant body because decrease of formic acid was not observed without the plant body (control).

[0052] (Formation of Carbon Dioxide by Administration of Formic Acid)

[0053] The extent of carbon dioxide produced by metabolism of formic acid was measured using rice plant bodies cultivated at 25° C. for two weeks as described above. The glass container containing 5 ml of 1.4 mM [¹²C] or [¹³C] sodium formate (pH7) was sealed by gumseptam and incubated at 25° C. under dark condition. Twenty-five μl of the solution was sampled at each period and content of carbon dioxide in the supernatant was analyzed by gas chromatography-mass spectrometry (GC-MS). As the result, 9% (FIG. 11A) or 1% (FIG. 11B) of [¹³C] CO₂, compared to total carbon dioxide, was detected in samples with addition of [¹²C] or [¹³C] formic acid, respectively, as shown in FIG. 11. As natural content of [¹³C] is about 1%, increased [¹³C] CO₂ would be originated from added formic acid. This result indicates existence of certain mechanism that converts formic acid to carbon dioxide in rice, for example, formate dehydrogenase (FDH).

[0054] (Measurement of FDH Activity)

[0055] Then the alteration of FDH activity by administration of formic acid was investigated. The rice plant bodies were cultivated in the presence or absence of 1.4 mM formic acid at 25° C. for two weeks. The aerial part and the ground part (root) was separated and the crude enzyme solution was prepared from each part. The enzyme solution was prepared to 1.5 mg/ml and FDH activities of the samples were measured. The FDH activity was measured using [¹³C] formic acid as the substrate and detecting [¹³C] CO₂ in the supernatant by GC-MS. When the root of rice was cultivated in the presence of formic acid, its activity was about twice compared to that of control group (without addition of formic acid), indicating increase of enzyme activity (FIG. 12).

[0056] (Isolation of RNA)

[0057] Isolation of total RNA was performed as described below. In the case of utilization for northern analysis, total RNA was isolated from leaf and root of rice cultivated under condition described above, using Isogen RNA purification kit (Nippon gene). In the case of cDNA preparation, total RNA was isolated using Plant RNA kit (QIAGEN). After treatment by DNAase, oligo(dT) 12-18 primer (GIBCOBRL) was used for reverse-transcription and cDNA was prepared.

[0058] (Cloning of cDNA Encoding FDH)

[0059] From sequence homology with FDH derived from potato, three clones of rice cDNA were selected from DDBJ (DDBJ accession nos. D23989, D23770 and D48722). The alignment of these cDNA clones revealed that, these cDNA sequences are constituting partial sequence of FDH homolog consisted of 970 bp. Then this partial sequence was cloned from rice cDNA using PCR. Using this sequence, full length of FDH gene was isolated using 3′- and 5′-Full Race core Set (Takara biochemicals).

[0060] (Determination and Analysis of the Base Sequence)

[0061] PCR products were subcloned to PCR2.1 (Invitrogen) or pUC18 (Takara biochemicals). The sequence of subcloned product was sequenced by DNA sequencer (ABI 310, Applied Biosystems), using M13 primer and sequencing kit (dye terminator cycle sequencing ready reaction kit, Perkin Elmer). The result showed that, the gene consists of a base sequence with reading frame of 1450 base pair (sequence list: sequence number 2). The sequence was analyzed using genetic-mac (genetic information processing software), a sequence analysis software. The result revealed that the deduced amino acid sequence of FDH consists of 376 base pair (sequence list: sequence number 1), with calculated molecular weight of 41.2 kDa and isoelectric point of 7.39. The sequence homology was compared between this sequence and FDH sequences originated from other known plants. The result exhibited high homology with known FDH sequences of other plants. That is, the amino acid sequence of rice (C.sativa) FDH exhibited high homology with potato (S.tuberosum: 82.7%) FDH and barley (H.vulgare: 91.7%) FDH. Moreover, the formic acid binding site (282) and the NAD binding site (189-223) were shown to be highly conserved among these plants (FIG. 13). As amino acid sequence of rice FDH and base sequence encoding the enzyme were determined, resistance against photo-oxidation damage might be rendered to a plant by incorporation of the gene described in sequence number 2 in the sequence list.

[0062] (Expression of cDNA in E.coli.)

[0063] The amino acid sequence deduced from the gene obtained by the cloning described above showed high homology with known FDH. Therefore, this sequence was expected to encodes FDH and the cDNA was expressed in E.coli to confirm the function of this sequence. The plasmid, utilised to be expressed in E.coli, was prepared by insertion of target fragment into pUC18 plasmid abscission. The fragment was prepared by PCR amplification using primers containing restriction enzyme recognition sites and then the product was treated by restriction enzyme. The fragment thus prepared was inserted into pUC18 plasmid. The primer containing EcoRI site and BamHI site was prepared in two series and the insertion fragments were prepared for two orientations. That is, insertion orientations of the sequence are sense orientation and anti-sense orientation. The primers used were 5′-cggaattcatggcgatgtggagggcggc-3′ (forward direction) and 5′-cgggatccttactggtactggc-3′ (reverse direction) for the sense orientation and 5′-cgggatccatggcgatgtggagggcg-3′ (forward direction) and 5′-cggaattcttactggtactggctcgcgagc-3′ (reverse direction) for the anti-sense orientation (Reverse). The PCR products using the primers were incorporated into pUC18 plasmid by EcoRI site and the BamHI site, to the initiation codon or the termination codon. The insertion of cloned sequence was confirmed by sequencing using di-deoxy method utilizing M13 primer.

[0064] The E.coli JM109 strain was transformed by the plasmid thus prepared. Transformed E.coli was cultured in 50 ml of LB medium (containing 50 mg/ml ampicillin) until the absorbance at 660 nm reached to 3.0. It was cultured under aerobic condition at temperature of 20° C., which is a lower temperature compared to ordinary condition. Then expression of protein was induced by 0.2 mM IPTG at 20° C. for 6 hours. The bacteria was collected, then washed by water and re-suspended into 2 ml of solution containing 10 mM SPB (pH 7.0), 100 mM NaCl, 0.5% triton X-100 and 2 mM DTT. The bacteria obtained was disrupted by sonication and the crude enzyme solution was prepared from supernatant of the centrifugation. The centrifugation was performed at 15,000 g for 15 min and the supernatant was obtained to measure enzyme activity. The intrinsic FDH of E.coli does not utilize NADH as a co-enzyme, as described in the report, the protein did not exhibit enzyme activity at the actual measurement. It was also revealed that, only the fragments with sense-orientated insertion exhibited enzyme activity. Therefore, it was strongly suggested that the sequence would be FDH protein with dependency to NAD.

[0065] (Alteration of FDH Gene Expression by Administration of Formic Acid)

[0066] The enzyme activity of rice FDH increased by administration of formic acid. Therefore, the expression of FDH gene, isolated in this experiment, was analyzed. Like measurement of enzyme activity, the rice plant was cultivated with or without formic acid. RNA was prepared from the aerial part and the ground part (root) respectively and the northern analysis was performed on these samples. Forty μg of the total RNA was applied to each lane and electrophoresis was performed on 1% agarose gel (containing 2.2 M formaldehyde). The gel was charged for the capillary blotting using Hybond N+ membrane (Amersham) using 20×SSC. The hybridization was performed according to instruction of AlkPhosDIREST (Amersham) and detection was performed using CDP-Star (Amersham). The FDH cDNA (open reading frame: 1130 bp), amplified by PCR, was used as probe DNA. The expression of FDH gene, measured on ground part of rice, exhibited significant increase by pretreatment with formic acid administration (FIG. 14).

[0067] As described above, a metabolite pathway described below exists in some plant species including rice. That is, methanol is metabolized to carbon dioxide by oxidation in a stepwise manner, through conversion to formaldehyde and formic acid as the intermediates. Then methanol, an alcohol with a low molecular weight, might be effective for inhibition of photo-oxidation damage and investigation was performed on the hypothesis. The plant bodies used in the experiment, the method to administrate sample substance, evaluation of photosynthesis by measurement of oxygen generation rate, photo-oxidation damage measurement and chlorophyl fluorescent measurement were performed as described in the experiments of formic acid.

[0068] (Effect of Methanol on Photosynthetic Ability of Rice)

[0069] By analysis of oxygen generation rate, effect of methanol on photosynthetic ability was investigated. The result indicated that, when oxygen generation rate of the control sample was reduced to 30%, the residual photosynthetic ability was 70% and 60% by addition of methanol and formate salt, respectively (FIG. 15). The dependency of light intensity was investigated after photo-oxidation damage of rice, using oxygen generation rate as an indicator (FIG. 16). The administration of methanol avoided photo-oxidation damage as shown in FIG. 16, especially under strong light illumination.

[0070] (Effect of Methanol on Chlorophyl Fluorescence Analysis of Rice Plant)

[0071] Furthermore, chlorophyl fluorescence analysis was performed under presence of various concentrations of methanol using rice. The addition of 25 mM or 50 mM methanol resulted in significant inhibition of reduction of Fv/Fm value caused by photo-oxidation damage (FIG. 17).

[0072] (Effect of Methanol on Chlorophyl Fluorescence Analysis of Tabacco and Kidney Bean)

[0073] Furthermore, the effect of methanol addition was also investigated on tabacco (FIG. 18) and kidney bean (FIG. 19). The chlorophyl fluorescence analysis revealed potency of 100 mM methanol addition, as the same as 2 mM formic acid addition. Then the damage on photo-system, caused by photo-oxidation damage, was significantly alleviated by addition of methanol.

[0074] A method to promote plant growth was proposed by this invention. It was achieved by administration of formic acid, an organic acid of low molecular weight, through avoidance of photo-oxidation damage. Moreover, amino acid sequence of formate dehydrogenase and base sequence encoding the enzyme were also proposed. In addition, a method to promote plant growth by administration of methanol, through avoidance of photo-oxidation damage, was proposed.

1 2 1 376 PRT Rice formate dehydrogenase VARIANT 287 Xaa = Any Amino Acid 1 Met Ala Met Trp Arg Ala Ala Ala Gly His Leu Leu Gly Arg Ala Leu 1 5 10 15 Gly Ser Arg Ala Ala His Thr Ser Ala Gly Ser Lys Lys Ile Val Gly 20 25 30 Val Phe Tyr Lys Gly Gly Glu Tyr Ala Asp Lys Asn Pro Asn Phe Val 35 40 45 Gly Cys Val Glu Gly Ala Leu Gly Ile Arg Glu Trp Leu Glu Ser Lys 50 55 60 Gly His His Tyr Ile Val Thr Asp Asp Lys Glu Gly Leu Asn Ser Glu 65 70 75 80 Leu Glu Lys His Ile Glu Asp Met His Val Leu Ile Thr Thr Pro Phe 85 90 95 His Pro Ala Tyr Val Ser Ala Glu Arg Ile Lys Lys Ala Lys Asn Leu 100 105 110 Glu Leu Leu Leu Thr Ala Gly Ile Gly Ser Asp His Ile Asp Leu Pro 115 120 125 Ala Ala Ala Ala Ala Gly Leu Thr Val Ala Glu Val Thr Gly Ser Asn 130 135 140 Thr Val Ser Val Ala Glu Asp Glu Leu Met Arg Ile Leu Ile Leu Leu 145 150 155 160 Arg Asn Phe Leu Pro Gly Tyr Gln Gln Val Val His Gly Glu Trp Asn 165 170 175 Val Ala Gly Ile Ala Tyr Arg Ala Tyr Asp Leu Glu Gly Lys Thr Val 180 185 190 Gly Thr Val Gly Ala Gly Arg Ile Gly Arg Leu Leu Leu Gln Arg Leu 195 200 205 Lys Pro Phe Asn Cys Asn Leu Leu Tyr His Asp Arg Leu Lys Ile Asp 210 215 220 Pro Glu Leu Glu Lys Glu Ile Gly Ala Lys Tyr Glu Glu Asp Leu Asp 225 230 235 240 Ala Met Leu Pro Lys Cys Asp Val Ile Val Ile Asn Thr Pro Leu Thr 245 250 255 Glu Lys Thr Arg Gly Met Phe Asn Lys Glu Arg Ile Ala Lys Met Lys 260 265 270 Lys Gly Val Ile Ile Val Asn Asn Ala Arg Gly Ala Ile Met Xaa Thr 275 280 285 Gln Ala Val Ala Asp Ala Cys Ser Ser Gly Gln Val Ala Gly Tyr Gly 290 295 300 Gly Asp Val Trp Phe Pro Gln Pro Ala Pro Lys Gly Pro Pro Trp Arg 305 310 315 320 Tyr Met Pro Asn His Ala Met Thr Pro His Ile Ser Gly Thr Thr Ile 325 330 335 Asp Ala Gln Leu Arg Tyr Ala Ala Gly Val Lys Asp Met Leu Asp Arg 340 345 350 Tyr Phe Lys Gly Glu Asp Phe Pro Val Gln Asn Tyr Ile Val Lys Glu 355 360 365 Gly Gln Leu Ala Ser Gln Tyr Gln 370 375 2 1450 DNA Rice formate dehydrogenase misc_feature 959, 1296 n = A,T,C or G 2 cgagtcggct gcactgatcg attccatcac tctctctctc tcgcctgctc gcggttgctg 60 tgcgttcgtc tcgcgatttc tcctcctcct cctgggatca tggcgatgtg gagggcggcg 120 gcggggcatc ttctcggccg cgcgctcggc tccagggccg cgcacacatc agcaggcagc 180 aagaagatcg tgggtgtgtt ctacaagggc ggcgagtacg ccgacaagaa tcccaacttc 240 gtcggctgcg tggagggcgc tctcggcatc cgcgaatggc ttgagtccaa ggggcatcac 300 tacattgtca ccgacgacaa ggaggggcta aacagcgagc tggagaagca cattgaggat 360 atgcatgtct tgatcaccac ccctttccac ccagcctatg ttagcgcaga aaggatcaag 420 aaggcaaaga acctcgagct gcttctcaca gctgggattg ggtcagatca tattgatctg 480 ccagcagctg ctgcagcagg tttaactgtg gcagaggtta ccggaagtaa cactgtgtcg 540 gtggcagaag atgagctcat gcgcattttg attttgctca ggaacttctt gcccgggtat 600 cagcaggttg ttcatggtga atggaatgtt gctggcattg cctatagggc ttatgatctt 660 gaaggaaaaa ctgtggggac tgttggggct ggtcgtattg gcaggctctt acttcagcgt 720 cttaagccct ttaactgcaa cctgctgtac catgacagac ttaaaattga cccagaactt 780 gagaaagaaa ttggggccaa atatgaagag gatctcgatg ctatgcttcc aaagtgtgat 840 gtcattgtga tcaatacacc tcttacagag aaaacaagag gtatgtttaa taaagaaaga 900 attgcaaaga tgaagaaagg tgtaatcatt gtgaataatg ctcgaggagc aatcatggnt 960 acccaggcgg ttgcagacgc ttgctctagt ggtcaagttg caggctatgg tggtgatgtc 1020 tggttccccc aaccagcacc aaagggtcca ccctggcggt acatgcctaa tcatgccatg 1080 acccctcata tctctgggac tacaattgat gcacagctga gatacgcagc aggagttaag 1140 gacatgctgg acaggtactt caaaggggaa gacttcccgg tgcagaacta catcgtcaag 1200 gaaggtcagc tcgcgagcca gtaccagtaa taacccttcc ttgtgtgttg ggtgtccatc 1260 ctgtggccac cttcccgcag ttaaggggaa cagagnttcg ggtagggacc aaaacaactt 1320 gtgttgttgt tgttgcctga gtgttccctg agaaactatt ggacaccgga aataatggat 1380 gcctgccatg gcaaccatgg ctccgaagaa taaaaagccc tcggattaaa cagtacaaaa 1440 aaaaaaaaaa 1450 

What is claimed is:
 1. A method to promote growth of a plant, the method comprising administration of an organic acid with a low molecular weight or its salt to a plant.
 2. The method according to claim 1, the method comprising administration of the organic acid or its salt to avoid photo-oxidation damage of the plant.
 3. The method according to claim 1, wherein said organic acid or its salt is formic acid or a formate salt.
 4. The method according to claim 3, wherein said formate salt is selected from the group consisted of potassium formate, sodium formate and ammonium formate.
 5. The method according to claim 3, the method comprising administration of the organic acid or its salt to induce enzyme activity of formate dehydrogenase.
 6. A plant yield promoting agent, the agent comprising an organic acid with a low molecular weight or its salt.
 7. The plant yield promoting agent according to claim 6, wherein said organic acid is formic acid or a formate salt.
 8. The plant yield promoting agent according to claim 7, the agent containing formic acid or a formate salt at the concentration of 125 ppm.
 9. The plant yield promoting agent according to claim 7, wherein the agent contains formic acid or a formate salt and has a pH adjusted to 5.5-8.0.
 10. The plant yield promoting agent according to claim 7, wherein said formate salt is selected from the group consisted of potassium formate, sodium formate and ammonium formate.
 11. A peptide fragment derived from rice formate dehydrogenase having an amino acid sequence of following (a) or (b): (a) an amino acid sequence referred to as amino acid numbers from 1 to 376 in sequence number 1 in a sequence list, (b) an amino acid sequence in which a part of said amino acid sequence (a) is deleted or another amino acid sequence is added to said amino acid sequence (a) or a part of said amino acid sequence (a) is substituted with another amino acid sequence, the amino acid sequence (b) exhibiting enzyme activity to synthesize carbon dioxide using formic acid as substrate.
 12. A DNA fragment derived from rice formate dehydrogenase having a base sequence of following (c) or (d): (c) a base sequence referred to as base numbers from 1 to 1450 in sequence number 2 in a sequence list, (d) a base sequence hybridizes with said base sequence (c) under stringent condition, the base sequence (d) encoding a protein exhibiting enzyme activity to synthesize carbon dioxide using formic acid as substrate.
 13. A method to promote growth of a plant, the method comprising incorporation of DNA fragment according to claim 12 into a plant and over-expression of formate dehydrogenase in the plant.
 14. A transgenic plant produced by incorporation of DNA fragment according to claim 12 into a plant and over-expression of formate dehydrogenase in the plant.
 15. A method to promote growth of a plant, the method comprising administration of an alcohol with a low molecular weight to the plant.
 16. The method according to claim 15, wherein said alcohol is methanol.
 17. The method according to claim 15, the method comprising administration of the alcohol to avoid photo-oxidation damage of the plant.
 18. A plant yield promoting agent containing methanol.
 19. The plant yield promoting agent according to claim 18, the agent containing methanol at a concentration of 50 mM 